JP3940562B2 - Compressor protection method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to the field of compressors used in refrigerators or heat pumps, and in particular to protecting the compressor by maintaining the compressor within its proper operating parameters.
[0002]
[Prior art]
The heat pump transfers heat (or energy) from a relatively low temperature side to a high temperature side using a refrigeration cycle. On the low temperature side, the refrigerant evaporates at a relatively low pressure. This turns the liquid into a vapor and extracts heat from a medium that may be air, water, brine, or the ground. The generated steam passes through one or more compressors, where the pressure rises. After exiting the compressor, the high pressure vapor flows into the condenser where it turns into a liquid. At this stage, heat is released from the refrigerant into the air, water, brine, or other medium that may be ground. The amount of heat released is approximately equal to the amount of heat extracted on the low temperature side plus the energy required to move the vapor refrigerant from the low pressure side (low temperature side) to the high pressure side (high temperature side).
[0003]
Since the refrigeration cycle of the heat pump can be reversed, this unit can be used for both heating and cooling. The refrigerant cycle in the two modes is basically the same.
[0004]
[Problems to be solved by the invention]
In order for a heat pump to operate efficiently, there must be a sufficient temperature difference between the refrigerant and the medium (such as air, water, brine, or surface). From an efficiency standpoint, it is desirable for a heat pump to supply more (thermal) energy than it consumes (electrical) energy.
[0005]
The center of the heat pump or refrigeration apparatus is a compressor. Each type of compressor has an associated compressor map, that is, an area function of saturated suction temperature and saturated discharge temperature. Manufacturers generally guarantee compressor reliability when the compressor is operating within its compressor map. Unfortunately, the compressor may operate outside the compressor map without the user being aware until it suddenly fails.
[0006]
[Means for Solving the Problems]
Briefly, the controller monitors the saturation suction temperature and saturation discharge temperature of a device that includes a compressor or a compressor that operates as part of a heat pump. If the compressor operates out of its compressor map, the controller controls to ensure that the compressor operates within that compressor map. Such a control operation includes defrosting the condenser coil and stopping power supply to the unit when the apparatus is in the heating mode.
[0007]
In one embodiment of the present invention, a method for protecting at least one compressor used in a heat pump or a refrigeration system includes: (a) determining a saturated suction temperature (hereinafter abbreviated as SST) of the at least one compressor; and (b) Determining a saturated discharge temperature (hereinafter abbreviated as SDT) of the at least one compressor; (c) determining first and second limits for the at least one compressor; and (d) for the at least one compressor. Defining first and second specific performance margins in relation to the first and second limits, and (e) based on the first and second limits and the first and second performance margins, Determine if at least one compressor is operating in the preferred area and take action if it is not operating in the preferred area Including the door.
[0008]
In one embodiment of the present invention, a method for protecting at least one compressor used in a heat pump or refrigeration system comprises: (a) determining a saturated suction temperature (SST) of the at least one compressor; and (b) at least one of the above. Determining a saturation discharge temperature (SDT) of one compressor; (c) defining first and second limits for the at least one compressor; and (d) first and second for the at least one compressor. A first and a second specific performance margin in relation to the limit of the compressor, and (e) comparing the SST with a specific temperature, and if the SST is lower than the specific temperature, the compressor operating in the device If there is, the power supply to one compressor is stopped, and if SST is above a certain temperature, SST is merged with the first limit and the first performance. (F) When SST is less than or equal to the sum of the first limit and the first performance margin, it is determined whether SST is higher than the first limit, and (g) SST is When higher than the sum of the first limit and the first performance margin, it is determined whether or not the condenser coil frost is larger than a specific ratio, and when it is larger than the specific ratio, the coil is defrosted. If it is not greater than a certain ratio, if there is a compressor operating in the apparatus, the power supply to one compressor is stopped, and (h) SDT changes when SST is less than or equal to the first limit. Determine if the rate is greater than a certain value, if not greater than a certain value, periodically determine whether the rate of change of SDT is greater than a certain value, and if greater than a certain value, Coil frost is a certain percentage If it is larger than a specific ratio, the coil is defrosted. If it is not larger than the specific ratio, if there is a compressor operating in the apparatus, the power supply to one compressor is reduced. And (i) when SST is higher than the first limit and SST is less than or equal to the sum of the first limit and the first performance margin , SDT reduces the second performance margin from the second limit. It is judged whether it is higher than the subtracted value, and when it is higher than this value , the power supply to the compressor is prohibited, and when it is not higher than this value , the power supply to the compressor is permitted if necessary. .
[0009]
DETAILED DESCRIPTION OF THE INVENTION
While the present invention is applicable to any type of heat pump or refrigerator, the following description focuses primarily on air-to-water heat pumps.
[0010]
Referring to FIG. 1, a general compressor map shows an operation region within parameters of a saturated suction temperature (hereinafter abbreviated as SST) and a saturated discharge temperature (hereinafter abbreviated as SDT). The area surrounded by the line is the safe operating area of a given compressor.
[0011]
In FIG. 2, the condenser 20 is in fluid communication with the evaporator 30 via an electronic expansion valve EXV. Steam from the evaporator 30 travels to the compressor 40 where it is liquefied and pressurized before entering the condenser 20. A converter 60, preferably a suction pressure converter, determines the suction pressure and converts the suction pressure to a saturated suction temperature SST based on a well-known simple linear relationship between the saturation pressure and the saturation temperature. The converter 70, which is preferably a discharge pressure converter, obtains the discharge pressure and converts this discharge pressure into a saturated discharge temperature SDT. A thermistor that reads the appropriate temperature directly can be used selectively, but the preferred pressure transducer is believed to be more accurate. SST and SDT are read by the controller 18. The controller 18 can be a microcontroller or CPU, can be pre-programmed for a particular compressor, and can be selectively programmed for different compressors as needed. It is.
[0012]
Referring to FIG. 3, the SST and SDT read by the control device 18 are processed according to the flowchart shown. In step 110, SST is measured every 15 seconds. The SST is compared at step 120 to a predetermined temperature, indicated as “X”, provided by the compressor manufacturer based on the compressor map of the particular unit being controlled. The values shown as “Limit 1”, “Limit 2”, “Y” (Steps 140, 150) and “Z” (Steps 160, 170) are also based on the compressor map. For example, in Carrier Corporation model number 30RH17 / 21/26/33/40/50/60/70/80/90/100/120/140/160/200/240, limit 1 = 68 ° F., limit 2 = 150 ° F, X = -4 ° F, Y = 10 ° F, Z = 2 ° F.
[0013]
If SST is less than or equal to X ° F., the power supply of one compressor is stopped in step 125. If SST is higher than X ° F, it is determined whether or not SST is higher than limit 1 by a predetermined value “Y”, as shown in step 140. If yes, as described in US patent application Ser. No. 09 / 525,348, filed simultaneously with the present application, the name “Defrost Control of Reversible Heat Pump”, the frost formation of the coil is confirmed in step 142. If the frost on the coil is greater than 75%, the coil is defrosted as shown at step 144. If the coil frost is less than 75%, the power supply to one compressor is stopped as shown in step 146.
[0014]
If SST is less than or equal to limit 1 + Y ° F in step 140, the value of SST is checked in step 150 to check whether SST is greater than limit 1. SST is lever cry at greater than limit 1, check the SDT rate of change in step 152, to determine whether greater than a certain value, such as for example 1.1 ° F / min. The exact value depends on the compressor being controlled. If the rate of change is greater than 1.1 ° F./min, then in step 154, the rate of coil frost formation is confirmed. If the rate of change is 1.1 ° F./min or less, the rate of change is checked again when the specific time shown as 3 minutes in FIG. If the coil frost rate is greater than 75% in step 154, the coil is defrosted in step 158. If the frost rate is not greater than 75%, the power supply to one compressor is stopped in step 156. To do.
[0015]
If SST is greater than limit 1, that is, if the compressor is operating within the normal SST range, whether SDT is higher than limit 2 minus safety margin “Z” in step 160 Judging. If YES, in step 162, power supply to the compressor is prohibited. If NO, as shown in step 170, the power supply to the compressor can be safely permitted as necessary.
[0016]
Thus, the present invention ensures that the compressor operates within the compressor map, i.e., is guaranteed by the manufacturer's warranty policy that guarantees compressor life and reliability.
[0017]
Although the present invention has been described with reference to certain preferred embodiments and the accompanying drawings, those skilled in the art will recognize that the invention is not limited to the preferred embodiments and is defined by the claims. Various changes and the like can be made without departing from the scope of the invention.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a general compressor map.
FIG. 2 is a schematic explanatory diagram of a refrigeration circuit.
FIG. 3 is a flowchart of the method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 18 ... Control apparatus 20 ... Condenser 30 ... Evaporator 40 ... Compressor 60 ... Suction pressure converter 70 ... Discharge pressure converter

Claims (3)

A method for protecting at least one compressor used in a heat pump or refrigeration system comprising:
Determining a saturated suction temperature of the at least one compressor;
Determining a saturated discharge temperature of the at least one compressor;
Determining a saturation suction temperature limit and a saturation discharge temperature limit for the at least one compressor;
A specific first performance margin and a second performance margin associated with units of saturation suction temperature and saturation discharge temperature, respectively ;
The saturated suction temperature as compared to a specific temperature that indicates the lower limit of the saturated suction temperature, if lower the saturation suction temperature than said specific temperature, if it is operated compressor within the device, one compressor When the load is removed and the saturated suction temperature is equal to or higher than the specific temperature, the saturated suction temperature is compared with the sum of the saturation suction temperature limit and the first performance margin,
If the saturation suction temperature is less than or equal to the sum of the saturation suction temperature limit and the first performance margin, determine whether the saturation suction temperature is higher than the saturation suction temperature limit;
If the saturation suction temperature is higher than the sum of the saturation suction temperature limit and the first performance margin, is the condenser coil frosting greater than a certain percentage that indicates a malfunction of the condenser coil ? determine whether, greater than said certain percentage and defrosting said coil, not greater than the certain percentage, if the compressor is operated in the device, the one compressor by dividing the load ,
Wherein when the saturation suction temperature is below the limit of the saturated suction temperature, rate of change of the saturation discharge temperature to determine whether greater than a certain value that indicates an abrupt change in the saturated discharge temperature, the specific value be greater than the rate of change of saturation discharge temperature so as to periodically determine whether greater than the specific value, the when greater than a certain value, forming frost of the coil of the specific The coil is defrosted if it is larger than the specific ratio, and if it is not larger than the specific ratio, one compressor is operated if a compressor is operated in the apparatus. Unload and
The saturated suction temperature is higher than the limit of the saturated suction temperature, and if the saturated suction temperature is below the sum of the first performance margin the limit of the saturated suction temperature, the saturation discharge temperature is the saturated It is determined whether the value is higher than the value obtained by subtracting the second performance margin from the discharge temperature limit . If it is higher, the load on the compressor is prohibited, and if not higher, the load on the compressor is allowed if necessary. A method for protecting a compressor, comprising: The first performance margin is 10 ° F.
2. The compressor protection method according to claim 1, wherein the second performance margin is 2 degrees Fahrenheit. A method for protecting at least one compressor used in a heat pump or refrigeration system comprising:
Determining a saturated suction temperature of the at least one compressor;
Determining a saturated discharge temperature of the at least one compressor;
Determining a saturation suction temperature limit and a saturation discharge temperature limit for the at least one compressor;
A specific first performance margin and a second performance margin associated with units of saturation suction temperature and saturation discharge temperature, respectively ;
Define the preferred operating region based on said limit and limit the first and second performance margins saturated discharge temperature of the saturated suction temperature of said at least one saturated suction temperature and saturated discharge temperature of the compressor is preferred wherein determining whether the operating area, if not the preferred operating region, or defrost the condenser coil, or if the compressor is operated in the device, dividing load one compressor A method for protecting a compressor, comprising:

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